Landing below glideslope?

[parrothead]

What is the reg that deals with landing below glideslope when landing is assured? If you're coming down the slope and have landing assured, is it legal to dip below the glideslope so you get it closer to the touchdown zone or do you have to stay on the slope all the way down? There are many versions of a "correct" answer. If anyone can find the reg, please post it. Thanks!!

 

[satpak77]

91.129 should answer your questions

 

[Wingman10]

Having flown 91,135 and121 operations, it seems this was more of an issue at the 91 and 135 level. In theory, not descending below glide path or VASI has something to do with the TCH for the wheel carriage clearence on the bigger jets.
Just an observation but for the most part in 121 operations this practice was not acceptable nor common practice has I had seen it before in previous 91 and 135 operators.
91.129 does give you some guidance on this issue but it still leaves room for some grey areas of interpetation.
I hope this helps.

 

[Rez O. Lewshun]

Any pilot with precison airmanship skills will control the aircraft energy, staying on either the ILS GS or visual glide path, all the way down to the 1000' marker.



Dipping below the GS or VASI is for amatuers.....

 

[DrewBlows]

Why would you want to go below glideslope?

 

[satpak77]

Any pilot with precison airmanship skills will control the aircraft energy, staying on either the ILS GS or visual glide path, all the way down to the 1000' marker.

Dipping below the GS or VASI is for amatuers.....

that is 100% correct, I agree 100% with that one!

 

[parrothead]

I ask this because sometimes the speeds are so conservative, that if you know your plane and know that the speeds are going to make you float, how to land in the touchdown zone nicely and not float too much. I am just asking what the legalities are, not what professional practices are. I know what professional practices are! Thanks for all of your comments!

 

[MauleSkinner]

Why would you want to go below glideslope?

If your book landing distance is 3600 feet, and you have 3900 feet of runway, dipping below glideslope to touch down at 500 feet from the threshold adds 500 feet to the runway available, increasing the margins.

Note that 91.129 says "until a lower altitude is necessary for a safe landing", not "when landing is assured". I'm sure everybody noticed, but I'm also big on stating the obvious, just in case

Fly safe!

David

 

[MauleSkinner]

I ask this because sometimes the speeds are so conservative, that if you know your plane and know that the speeds are going to make you float, how to land in the touchdown zone nicely and not float too much. I am just asking what the legalities are, not what professional practices are. I know what professional practices are! Thanks for all of your comments!

As far as float goes, if you know your airplane is going to float at the appropriate speed, just reduce to idle sooner and follow the glideslope.

Fly safe!

David

 

[twepilot]

And flying below the GS is safe??!!

RV

 

[DrewBlows]

If your book landing distance is 3600 feet, and you have 3900 feet of runway, dipping below glideslope to touch down at 500 feet from the threshold adds 500 feet to the runway available, increasing the margins.

I suppose this is reasonable. I can't relate to this situation though, as I have never had to cut it that close. (Part 121 gives you generous margins, for those of us who slipped though the cracks.)

 

[minitour]

If your book landing distance is 3600 feet, and you have 3900 feet of runway, dipping below glideslope to touch down at 500 feet from the threshold adds 500 feet to the runway available, increasing the margins.

Is that even legal under 121 or 135? Does that meet the 60% (or is it 70%?) requirements? (I always mix the 60%/70% up).

-mini

 

[avbug]

§ 91.129 Operations in Class D airspace.

(e) Minimum Altitudes. When operating to an airport in Class D airspace, each pilot of -

(2) A large or turbine-powered airplane approaching to land on a runway served by an instrument landing system (ILS), if the airplane is ILS equipped, shall fly that airplane at an altitude at or above the glide slope between the outer marker (or point of interception of glide slope, if compliance with the applicable distance from clouds criteria requires interception closer in) and the middle marker; and

(3) An airplane approaching to land on a runway served by a visual approach slope indicator shall maintain an altitude at or above the glide slope until a lower altitude is necessary for a safe landing.

Remember that operations under Parts 121 and 135 are also beholden to Part 91. Parts 119, 121, and 135 merely add additional restrictions to the general operating regulations.

 

[MauleSkinner]

Is that even legal under 121 or 135? Does that meet the 60% (or is it 70%?) requirements? (I always mix the 60%/70% up).

-mini

I don't know about 121, but the 60% rule under 135.385 is only a "takeoff" requirement, not a "landing" requirement. In other words, if things change enroute, you can still land.

It can also be pretty much disregarded under paragraph (e), provided you have an appropriate alternate:

A turbojet airplane that would be prohibited from being taken off because it could not meet paragraph (b)(2) of this section (the 60% rule) may be taken off if an alternate airport is selected that meets all of paragraph (b) of this section.

Fly safe!

David

 

[THE Flying Ace]

Based out of FCM (Flying Cloud in Minneapolis) where the runway is only 3900 feet, it is common to dip below and aim for the numbers. Everytime we come home, it is like doing a short field approach. I wish MAC would just do this runway extention that they have been talking about for many years.

 

[minitour]

I don't know about 121, but the 60% rule under 135.385 is only a "takeoff" requirement, not a "landing" requirement. In other words, if things change enroute, you can still land.

It can also be pretty much disregarded under paragraph (e), provided you have an appropriate alternate:

Fly safe!

David

ooooooh...now I get it.

Ya the gleim ATP test prep doesn't really do that reg justice. I get it tho...so I can legally land in that amount of distance...I just can't takeoff in the first place unless my performance numbers (taking into account normal fuel/oil consumption) allow for a landing in 60% of the available (or is it "usable"?) runway.

Very good.

Thanks...dang that clears a lot up...

Back to the question though...
If your numbers show you can land in X feet (3,000 as an example) and the runway is Y (3200) feet long... you should be plenty good to go. Doesn't the landing performance data include crossing the threshold at 50' and touching down on GS?

-mini

 

[MauleSkinner]

Back to the question though...
If your numbers show you can land in X feet (3,000 as an example) and the runway is Y (3200) feet long... you should be plenty good to go. Doesn't the landing performance data include crossing the threshold at 50' and touching down on GS?

-mini

Yes, you are, and yes, it does...BUT...have you ever stopped 200 feet short of the end of the runway with max braking? It's not fun...I'll take every advantage I can get.

Fly safe!

David

 

[minitour]

Yes, you are, and yes, it does...BUT...have you ever stopped 200 feet short of the end of the runway with max braking? It's not fun...I'll take every advantage I can get.

Fly safe!

David

LOL actually....this one time flying my first SE Approach in a Duchess (damn prop wouldn't unfeather)...I was just....a LITTLE fast and uh...

Runway 3 at OUN never seemed so short...we did finally make Bravo though...I had the instructor almost crapping

True...not fun and yes you're right...take every single advantage.

-mini

 

[MauleSkinner]

LOL actually....this one time flying my first SE Approach in a Duchess (dang prop wouldn't unfeather)...I was just....a LITTLE fast and uh...

Runway 3 at OUN never seemed so short...we did finally make Bravo though...I had the instructor almost crapping

True...not fun and yes you're right...take every single advantage.

-mini

You can tell it's a guy's first real engine-out landing in a twin just by watching...almost everybody does it that way

 

[avbug]

Back to the question though...
If your numbers show you can land in X feet (3,000 as an example) and the runway is Y (3200) feet long... you should be plenty good to go. Doesn't the landing performance data include crossing the threshold at 50' and touching down on GS?

That was a joke, right??

 

[jetfo]

Remember that operations under Parts 121 and 135 are also beholden to Part 91. Parts 119, 121, and 135 merely add additional restrictions to the general operating regulations.

Clearly this means you should stay on GS at least until the MM and then proceed visually as required. You can also follow the VASI/PAPI at that point.

 

[avbug]

Clearly this means you should stay on GS at least until the MM and then proceed visually as required.

Not should. Must. You are required to remain on or above the glideslope between the outermarker and middle marker. This isn't optional.

See 14 CFR 91.129(e)(2)

You can also follow the VASI/PAPI at that point.

Not can. Must. You are remain at or above the glideslope when approaching to land at a runway served by a visual approach slope indicator.

See 91.129(e)(3).

You are required to remain above the visual glidepath until descent below it is necessary for a safe landing.

 

[minitour]

That was a joke, right??

Did it make you chuckle?

-mini

 

[avbug]

It might, if only otherwise-professionals didn't believe that sort of thing, to say nothing of the students and novices killed every year because an otherwise-professional taught it to them. It's a joke, right?

 

[Catbert]

You are required to remain above the visual glidepath until descent below it is necessary for a safe landing.

I think this is the crux of the matter. It's clearly legal to descend below the visual glidepath when necessary for a safe landing. So, the real question is: when is it necessary, if ever?

 

[avbug]

When it's safer to go below and use all the runway than it is to waste the runway and land down a third of it.

When is it safe to go below...when you have obstacles in sight, and can, in your professional judgement, do so.

In the summer time, I shoot to land well short of the runway and my wheels touch the tarmac on the end...I don't waste any. I'd sure feel like an idiot needing runway and leaving it behind.

Other types of operations, I don't do that...but some, I do. Where it's necessary, and appropriate. The airplane isn't on rails; it's flexible, and can be made to do what one needs it to do. Safely, professionally, and legally.

The circumstance dictates, as always.

 

[Slippery Mick]

What is the reg that deals with landing below glideslope when landing is assured?

I'm not sure. But I recommend never, ever trying to land above the glideslope. Those last few feet really, really hurt.

 

[Blackjet]

There is not just 1 correct answer for this question. He didn't state what the conditions were. In IMC, deviating from the GS is foolish, especially going below it. When the WX and VIS is down, there ar ejust not enough visual cues to judge height safely. If you are runway limited, maybe the conditions are not suitable to be landing at that particular field. Staying on the GS puts you 1000 feet down the runway. Can you afford to eat that 1000 feet?

On the other hand, there are several instances where getting off the GS would be smart. A flaps Zero landing (in a JET) is one of those instances. A visual approach backed up with an ILS is just that, a visual approach, and you are under no requirement to fly the GS down. Finally, being runway limited in VMC would be another instance where flying below the GS would be something to consider.

 

[MauleSkinner]

There is not just 1 correct answer for this question. He didn't state what the conditions were.

In reality he did...he asked about going below glideslope "when the landing is assured", which most of us have taken to mean he can see the runway.

On the other hand, there are several instances where getting off the GS would be smart. A flaps Zero landing (in a JET) is one of those instances. A visual approach backed up with an ILS is just that, a visual approach, and you are under no requirement to fly the GS down. Finally, being runway limited in VMC would be another instance where flying below the GS would be something to consider.

You might doublecheck 91.129(e)(2) for airports in Class D airspace:

A large or turbine-powered airplane approaching to land on a runway served by an instrument landing system (ILS), if the airplane is ILS equipped, shall fly that airplane at an altitude at or above the glide slope between the outer marker (or point of interception of glide slope, if compliance with the applicable distance from clouds criteria requires interception closer in) and the middle marker; and

The only exception you'd get is if you considered the no-flap landing an emergency, unlike using the visual approach slope indicator in paragraph (e)(3):

An airplane approaching to land on a runway served by a visual approach slope indicator shall maintain an altitude at or above the glide slope until a lower altitude is necessary for a safe landing.

Fly safe!

David

 

[Blackjet]

In reality he did...he asked about going below glideslope "when the landing is assured", which most of us have taken to mean he can see the runway.

Well, landing assured does not mean the runway can be seen. That is called runway in sight. I dont think any instructor has told you or anyone else that "landing assured means runway can be seen. Landing assured is when you can pull the power to idle or loose all propulsion and make the runway, not just the field. For example, when flying a single engine approach with an aircraft with 2 or more engines, the last increment of flaps is usually held until landing is assured. That would mean just about at the runway. That is where my confusion was as to his situation.

You might doublecheck 91.129(e)(2) for airports in Class D airspace:

You got me there. I was not familiar with that regulation, but I did look it up and indeed you are correct.

The only exception you'd get is if you considered the no-flap landing an emergency, unlike using the visual approach slope indicator in paragraph (e)(3):
Fly safe!

David

Personally, in most situations I would NOT consider 0 flaps an emergency, nor do I think it justifies an emergency, once again, in most cases, but not all. 0 Flaps is one of those situations where you are going to have to use superior judgement that usually keeps you out of situations that would require use of your superior skiils, but in this case, both are going to have to be present in order to have a desire outcome. Good luck to you as well, and thanks for the heads up on the "D" FAR.